Tiny specks of trouble

Harvard Health Letters

Anyone who's yearned for a clean house can attest to the seemingly supernatural properties of dust. No sooner have you banished it from the bookshelf than it peeks out from under the bed, shape-shifting from powdery and puffy to sticky and stringy. But the menace of dust can extend beyond the realm of housekeeping and damage your health in serious ways.

What is dust?

About 60 percent of household dust comes from soil tracked inside on the bottoms of shoes or the paws of pets or as airborne particles that have wafted through doors, windows and other openings. The remaining 40 percent is a hodgepodge of substances that originate inside the dwelling, including skin cells, pet fur, insect residue, carpet fibers and kitchen grease.

In dry, windy climates, people contend with layers of fine silt, and in cities, dust often has a sooty quality from car exhaust and other sources of air pollution.

It can be toxic …

Heavy metals and other poisons can linger in the environment for years and make their way into the dust in your home, explains David Layton, a researcher at the University of Arizona who's developed a computer model to track the migration of contaminated soil. His research, which has involved examination of dust samples from homes in California and the Midwest, has found measurable amounts of arsenic and lead from decades-old auto emissions and defunct coal-fired power stations.

Other research has shown the concentration of pollutants in households to be much higher (two to 23 times higher) than the concentrations in the surrounding soil. And the house doesn't need to be next door to a Superfund site, either. Wind and weather can loft toxic particles into the atmosphere and deposit them hundreds of miles away.

The dust generated inside a house also has its hazards. One study that looked at dust from 70 homes across the country identified more than three dozen chemicals that have been linked to immune system disorders and birth defects in laboratory animals. The chemicals come from flame retardants, pesticides, plastics and other compounds found in furnishings, electronics, cosmetics, adhesives, textiles and a variety of familiar consumer products. The chemicals rub or flake off in amounts that are usually too tiny to see or smell.

… and unseen

Dust can also be home to a thriving community of bacteria, fungi and minute spiderlike insects called dust mites that feed on dead skin cells. The debris they leave behind can provoke a powerful allergic reaction. As many as 500 mites can live in a single gram of dust, each of them producing many allergy-inducing droppings.

Endotoxins, substances released from the cell membranes of dust-dwelling bacteria, are another component of dust. A study conducted by the National Institute of Environmental Health Sciences evaluated endotoxin levels in over 2,500 dust samples from homes around the country. Results showed that adults who live in residences with increased concentrations of endotoxins reported higher rates of wheezing and other asthma symptoms. The effect was most pronounced in cases where endotoxin levels were elevated in bedrooms.

Exposure realities

On average, Americans spend more than two-thirds of their time at home inside, so we spend a lot of time in and near the dust in our homes. The most vulnerable family members are the youngest: infants, whose organs are still developing, are up to 100 times more susceptible to the health hazards of dust-borne pollutants than adults are.

Dust and the toxins it contains enter the body in one of two ways — people breathe it in or swallow it. Very small particles floating in the air can be inhaled deeply into the lungs and get into the blood. They've been associated with heart attacks and a host of other cardiovascular problems. Larger particles can cause serious, even life-threatening, problems for people with asthma and allergies. For most people, though, many dust particles are too large to get deep into the lungs.

So in many cases, the bigger danger in most cases is probably from swallowing dust. But who does that? Young children, of course, put many things into their mouths. Even in clean homes, talcum-size dust particles float around and land on surfaces and objects of oral interest to the young. Dust particles that size can also adhere to adult hands and be transferred to food inadvertently as we eat and cook.

Distributed by Tribune Media Services

What you can do

•Put heavy-duty doormats in front of the doorways to stem the amount of soil coming into a house. Even better: Remove your shoes before coming inside.

•Use filters on heating and air conditioning systems. Change filters every three months of active use. Portable air cleaners with high-efficiency particulate air (HEPA) filters are another option for filtering out extremely small particles.

(Note: Air purifiers may emit small amounts of ozone, a gas that can worsen asthma symptoms and may have other bad health effects. Many of these machines now have ozone-to-oxygen converters designed to decrease ozone emission.)

•Vacuum at least once a week, preferably with a vacuum cleaner with a HEPA filter.

•Clean higher surfaces first and then work your way down. Wipe floors and hard surfaces with a damp cloth or sponge. You can also use products like Grab-it or Swiffer that are treated to attract dust.

•Use chemical household cleaners in moderation, as most haven't been tested extensively for toxicity.